Compressor crank case venting arrangement for eliminating lube oil carryover

ABSTRACT

A reciprocating air compressor is provided with a modified valve plate to block the crank case from direct access to the intake manifold and a crank case vent tube coupled to the intake manifold opens to the crank case on the side of a coalescent separator opposite that having access to the reciprocating piston, thus preventing the oil-air mist, resulting from blowby in the crank case, to mix with the suction air being compressed by the compressor, prior to removal of the entrained oil.

United States Patent [191 Bulkley et al.

1 COMPRESSOR-CRANK CASE VENTING ARRANGEMENT FOR ELIMINATING LUBE OIL CARRYOVER [75] Inventors: Clifford T. Bulkley, Glastonbury;

David N. Shaw, East Granby, both of Conn.

[73] Assignee: Dunham-Bush, Inc., West Hartford,

Conn.

[22] Filed: May 8, 1973 [21] Appl. No.: 358,443

[52] US. Cl. 417/313, 92/79 [51] Int. Cl. Fl5b 2l/04, F04b 21/06 [58] Field of Search 417/437, 313; 92/79 [56] References Cited UNITED STATES PATENTS 2,178,662 11/1939 Hanson 92/79 2,204,814 6/1940 Newell 92/79 Maniscalco 92/79 Primary Examiner-William L. Freeh Attorney, Agent, or Firm-Sughrue, Rothwell, Mion, Zinn & Macpeak [5 7] ABSTRACT 3 Claims, 2 Drawing Figures COMPRESSOR CRANK CASE VENTING ARRANGEMENT FOR ELIMINATING LUBE OIL CARRYOVER BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to reciprocating gas compressors, and more particularly to air compressors in which the crank case is vented to the intake manifold to reduce crank case pressure produced by gas blowby.

2. Description of the Prior Art In self-contained motor compressor units for compressing air and other gases, it is conventional to collect lubricating oil within the crank case of the compressor, which is then fed under pressure to portions of the compressor for proper lubrication of the moving parts during compressor operation. In reciprocating compressors, the piston which normally reciprocates along the axis of its fixed cylinder and carries one or more piston rings which tend to retain a given amount of lubricating oil between the stationary cylinder walls and the reciprocating piston. During compression of the air, by reciprocation of the piston, the developed air pressure, regardless of the fit between the piston or rings and the compressor result in a certain amount of gas blowby which increases gas pressure within the crank case in the absence of venting means.

One method of venting the crank case, in the past, consists of porting the crank case to the air intake manifold of the compressor head. Reference to FIG. 1 illustrates one specific prior art arrangement for venting the crank case to the incoming gas to be compressed. Referring to this FIG., the gas compressor identified generally at 10, which is only partially shown, comprises a housing 12, including an end wall 14 at its right hand end, which supports by means of journal bearing 16, a compressor crank shaft 18 mounted for rotation about a horizontal axis. Crankshaft I8 is supplied with one or more connecting rods 20, each of which supports a piston 22 mounted for reciprocation within a stationary cylinder 24 formed integrally with the housing 12. Each piston 22 carries oil ring 23. The head of piston 22 defines a working chamber 25 between the head of the piston and a valve plate 26 which lies intermediate of the housing 12 and the head 27 of the compressor. In this respect, the head 27 defines for each piston and cylinder separate fluid passages in the form of an intake manifold 28 and an exhaust manifold 30. Communication between manifolds 28 and 30 and the working chamber 25 is controlled by valves (not shown) associated with the valve plate 26 for each cylinder. In this respect, however, a port or opening 32 permits fluid communication between intake manifold 28 for instance, and the chamber 25. Oil 40 generally accumulates to the level shown within crank case 38 beneath the crank shaft 18. Housing 12 is further provided with an attached end plate 42 which further carries a journal bearing 44 for additionally supporting the crank shaft 18. Plate 42 is bolted to the housing I2 by means of a number of bolts 46 as shown and effects a fluid sealed connection therewith. Plate 42 defines with end wall 14, an air intake passage 47. The end plate 42 effectively further acts to maintain a vertical suction screen 49 in position so as to separate a passage 47 formed by housing 12 and end plate 42 into inner and outer chambers 48 and 50 respectively. In this respect, assuming that the gas being compressed is air, air enters the air compressor through an air inlet fitting 52 into the outer chamber 50 and passes through the suction screen 49 to enter the inner chamber 48. A coalescent separator 70 consisting of a perforated annular plate 71 and a felt annulus 73 separates oil and other liquids carried by the incoming gas stream A. End wall 14 of housing 12 is provided with an opening 34 at the bottom which carries a check valve 36 which permits oil to drain into the bottom of the crank case 38. The end wall I4 of housing 12 is further provided with port 56 lying well above the level of the lube oil 40. Port 46 permits the oil-air mist M within crank case 38 to merge with the incoming air stream A, within inner chamber 48. Further, in the illustrated prior art arrangement, aligned openings 58 and 60 of housing 12 and the valve plate 26 respectively permit the incoming air and the oil-air mist emanating from port 56 to enter the intake manifold 28 for compression due to the reciprocation of piston 22. Unless the oil is recovered after compression exterior of the compressor, the available oil supply to the compressor is rapidly reduced.

SUMMARY OF THE INVENTION The invention is directed to modification of such reciprocating gas compressors such that the intake manifold is shut off from direct access to the crank case and the gas such as air being compressed is ported directly to the intake manifold while the crank case vent line fluid connects the air inlet upstream of the intake manifold or the manifold itself to the crank case to one side of a coalescent oil separator opposite that having access to the developed oil mist within the crank case. Thus, the oil-air mist resulting from gas blowby to the crank case impinges on the coalescent separator, the oil is separated and returned to the crank case, permitting only the crank case air minus the oil to enter the intake manifold after oil removal, and eliminating any possibility of lube oil carryover to the compressor dis charge.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a sectional elevational view of a portion of a prior art air compressor employing crank case venting.

FIG. 2 is a sectional, elevational view of the air compressor of FIG. I modified in terms of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 2, like elements to those illustrated in the prior art compressor of FIG. I carry like numerical designations. In this respect, compressor III of the present invention includes a housing 12 having an end wall 14 which defines in conjunction with head 27 a crank case 38 within which oil 40 rises to a given level. Again, the end wall 14 carries a journal bearing 16 supporting crank shaft 18 for rotation about a horizontal axis, the crank shaft being connected via connecting rod 20 to a piston 22 which reciprocates in similar manner to the arrangement of the compressor of FIG. I along its vertical axis within cylinder 24. The compressor may include two or more reciprocating pistons 22, as desired. An end plate 42 defines with end wall 14 of the housing 12 dual chambers 48 and 50 separated by coalescent separator 70.

Coalescent separator 70 in the compressor of FIG. 2 is identically arranged and as such comprises a perforated annular plate 71 which is sandwiched between casing 12 and end plate 42 and supports on the side of chamber 50 a felt annulus 73 permitting oil to be removed from the oil mist during passage from chamber 48 to chamber 50 which oil drains through check valve 36 to the crank case 38.

Further, the end plate 42 is provided with a journal bearing 44 further supporting the outer end of the crank shaft 18, the end plate 42 being coupled to the housing 12 by a series of bolts as at 46 in a fluid sealed manner.

The modification of the compressor in terms of the present invention further takes the form of a modified valve plate 72, which effectively covers the passage or opening 58 within housing 12 normally leading to intake manifold 28 although plate 72 is provided with a port atl32 permitting fluid connection between'intake manifold 28 and the working chamber defined by the head of piston 22, the wall of cylinder 24 and the modified valve plate 72. The intake and exhaust valves for the compressor are not shown. Further, in conjunction with the present invention, a fitting 74 fluid couples the chamber 50 to tube 76 which ports directly to the intake manifold 28. Tube 76 acts as the air inlet to the compressor (assuming air is the working fluid of the compressor). The crank case vent line indicated schematically at 78 constitutes in turn a small diameter tube leading from fitting 74 to the air inlet tube 76. Thus, essentially, the modified valve plate 72 effectively blocks the chamber 48 from direct access to the intake manifold except via chamber 50, and tube 78. The modified head 27 without communicating with the crank case in the fashion of the prior art arrangement is therefore not contaminated by the oil-air mist emanating from the crank case through check valve 36 leading into the inner chamber 48. The air leakage past the piston ring 23 and conventionally termed gas blowby creates an oil-gas mist which vents to the head 27 only after passage through the inner chamber 48, depositing the oil from the mist on the coalescent separator 70, whereupon the oil drains into the bottom of these chambers and passes through check valve 36 back into the crank case 38. Further, the air in passing from inner chamber 48 to outer chamber 50 moves through the coalescent separator 70 under very low velocity insuring the full removal of the oil prior to passing via fitting 74 and tube 78 to the air inlet tube 76 leading into the intake manifold 28. This results in the maintaining of a suitable oil supply 40 within the crank case 38 permitting the compressor to be efficiently lubricated and without the necessity of an external oil separator downstream of the compressor.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. In a reciprocating gas compressor comprising:

a compressor housing including a crank case for housing the compressor crank shaft and having at least one piston supported by said crank shaft and reciprocating within a fixed cylinder and defining with said cylinder a working chamber,

a vertical housing end wall defining a crank case vent passage separate from and to the side of said crank case,

an intake manifold overlying said compressor housing and being ported to said working chamber,

a coalescent separator vertically mounted within said crank case vent passage and spaced from said end wall to separate said crank case vent passage into a first chamber underlying said intake manifold and a second chamber,

a first vertical opening within said first chamber leading directly from said crank case vent passage first chamber into said intake manifold, and

a second opening within said housing second chamber for normally introducing the gas to be compressed to said second chamber for passage through said coalescent separator to remove oil carried thereby,

a first opening within the bottom of said end wall and carrying a check valve to permit oil flow from said first chamber into said crank case, and

a second opening within said end wall above said check valve opening for permitting oil-air mist within said crank case to vent from said crank case into said crank case vent passage first chamber, the improvement comprising:

means for blocking said first opening within said first chamber,

means for directing the intake gas to said compressor directly to said intake manifold, bypassing said first and second chambers, and

means for fluid coupling said second housing opening directly to said intake manifold,

whereby; the oil-air mist within the crank case entering said first chamber from said crank case, passes through said coalescent separator to remove the oil therefrom to permit venting of the crank case gas resulting from blow-by to the intake manifold, and returns the removed oil back to the crank case through said check valve to eliminate compressor lube oil carryover.

2. The compressor as claimed in claim 1, wherein said working chamber is defined by said at least one cylinder, the piston reciprocating therein, a valve plate overlies the cylinder and separates said head from said compressor housing, and defines with said cylinder and the head of said piston the working chamber, and said first opening comprises aligned openings within said valve plate and said compressor housing, and said means for blocking said first opening comprises a solid portion of said valve plate which overlies the opening within said compressor housing normally leading to said head.

3. The compressor as claimed in claim 2, wherein said working chamber is defined by said at least one cylinder, the piston reciprocating therein, a valve plate overlies the cylinder and separates said head from said compressor housing, and defines with said cylinder and the head of said piston the working chamber, and said first passage means comprises aligned openings within said valve plate and said compressor housing, and said means for blocking said first passage means comprises a solid portion of said valve plate which overlies the opening within said compressor housing normally leading to said head. 

1. In a reciprocating gas compressor comprising: a compressor housing including a crank case for housing the compressor crank shaft and having at least one piston supported by said crank shaft and reciprocating within a fixed cylinder and defining with said cylinder a working chamber, a vertical housing end wall defining a crank case vent passage separate from and to the side of said crank case, an intake manifold overlying said compressor housing and being ported to said working chamber, a coalescent separator vertically mounted within said crank case vent passage and spaced from said end wall to separate said crank case vent passage into a first chamber underlying said intake manifold and a second chamber, a first vertical opening within said first chamber leading directly from said crank case vent passage first chamber into said intake manifold, and a second opening within said housing second chamber for normally introducing the gas to be compressed to said second chamber for passage through said coalescent separator to remove oil carried thereby, a first opening within the bottom of said end wall and carrying a check valve to permit oil flow from said First chamber into said crank case, and a second opening within said end wall above said check valve opening for permitting oil-air mist within said crank case to vent from said crank case into said crank case vent passage first chamber, the improvement comprising: means for blocking said first opening within said first chamber, means for directing the intake gas to said compressor directly to said intake manifold, bypassing said first and second chambers, and means for fluid coupling said second housing opening directly to said intake manifold, whereby; the oil-air mist within the crank case entering said first chamber from said crank case, passes through said coalescent separator to remove the oil therefrom to permit venting of the crank case gas resulting from blow-by to the intake manifold, and returns the removed oil back to the crank case through said check valve to eliminate compressor lube oil carryover.
 2. The compressor as claimed in claim 1, wherein said working chamber is defined by said at least one cylinder, the piston reciprocating therein, a valve plate overlies the cylinder and separates said head from said compressor housing, and defines with said cylinder and the head of said piston the working chamber, and said first opening comprises aligned openings within said valve plate and said compressor housing, and said means for blocking said first opening comprises a solid portion of said valve plate which overlies the opening within said compressor housing normally leading to said head.
 3. The compressor as claimed in claim 2, wherein said working chamber is defined by said at least one cylinder, the piston reciprocating therein, a valve plate overlies the cylinder and separates said head from said compressor housing, and defines with said cylinder and the head of said piston the working chamber, and said first passage means comprises aligned openings within said valve plate and said compressor housing, and said means for blocking said first passage means comprises a solid portion of said valve plate which overlies the opening within said compressor housing normally leading to said head. 